Metal organic compounds and their use

ABSTRACT

Metal organic compounds containing both cobalt and nickel bound to boron are effective adhesion promoters for bonding rubber to brass-coated metal used as a reinforcement.

This is a division of application Ser. No. 08/491,199, filed Jun. 16,1995 now U.S. Pat. No. 5,607,996.

This invention relates to metal organic compounds, compositionscontaining them, and their use.

Compounds containing three atoms of a divalent metal such as cobalt,each linked through oxygen atoms to a boron atom and comprisingmonocarboxylic acid residues bonded to the metal are known additives forincorporation into rubber skim stock to improve adhesion of the rubberto brass-coated reinforcing wires.

European specification No. 0,148,782 describes metal organic compoundsof this kind made by heating at 100° C. to 250° C. a nickel or cobaltsalt of a carboxylic acid of from 3 to 24 carbon atoms with an alkalineearth metal borate.

European specification No. 0,150,840 describes cobalt boron compounds ofthe formula:

    B(OCOY).sub.3

where Y is the residue of a resin acid, a naphthenic acid or analiphatic carboxylic acid of 7 to 24 carbon atoms.

European specification No. 0,466,448 describes metal organic compoundsof formula:

    X(OMA'.sub.p).sub.m (OMB'.sub.p).sub.n

where X is boron or phosphorus, M is cobalt, nickel or bismuth, B' is aresidue of aromatic carboxylic acid of 7 to 11 carbon atoms, A' is aresidue of an aliphatic carboxylic of 7 to 11 carbon atoms, p is 1 or 2,n is 0.5 to 2, and m is (3-n).

In these known compounds the preferred metal is cobalt which is known toprovide the best performance in the stated utility of improving adhesionof rubber to brass-coated steel, used as a reinforcement.

Nickel is known to give products which have inferior properties to thosecontaining cobalt. Nevertheless, because nickel is ordinarily cheaperthan cobalt, the possibility of replacing part of the cobalt by nickelhas been investigated.

One of the present inventors, in a paper presented to the RubberDivision of the American Chemical Society in New York, U.S.A. in April1986, presented data showing that if a nickel boron acylate is mixedwith a cobalt boron acylate in a cobalt: nickel ratio of 2:1, while theperformance of the mixture expressed as a percentage of the performanceof the pure cobalt compound was reduced to 96%, the cost of the mixtureat the then prevailing prices of cobalt and nickel, was reduced to 91%.Thus, it appeared that replacing a proportion of the cobalt by nickelmight present cost advantages, though only at the expense of theperformance of the product.

It has now surprisingly been discovered that although a mixture ofcobalt and nickel compounds of the above mentioned kind is, as alreadystated, inferior to pure cobalt containing compounds, compounds in whichcobalt and nickel are combined in a single molecule have superiorperformance to those containing cobalt only.

The compounds of the present invention may be represented by theformula:

    B(OCoA).sub.m (ONiA).sub.3-m

where the A radicals are the same or different and each in a residue ofan aliphatic monocarboxylic acid of 7 to 24 carbon atoms, a resin acid,a naphthenic acid, or an aromatic carboxylic acid of 7 to 11 carbonatoms, not more than two thirds of the A radicals being a said aromaticcarboxylic acid residue, and m is 0.5 to 2.5, preferably about 2.

The monocarboxylic acid used in the metal organic compounds of thepresent invention may be, for example, a monocarboxylic aliphatic acid,e.g. pentanoic acid, 2,2-dimethylpentanoic acid, 2-ethylpentanoic acid,4,4-dimethylpentanoic acid, n-octanoic acid, 2,2-dimethylhexanoic acid,2,2-ethylhexanoic acid, 4,4-dimethylhexanoic acid,2,4,4-trimethylpentanoic acid, n-nonanoic acid, 2,2-dimethylheptanoicacid, 3,5,5-trimethylhexanoic acid, n-decanoic acid,2,2-dimethyloctanoic acid, 7,7-dimethyloctanoic acid, n-undecanoic acid,a mixture of 2,2,2-trialkyl acetic acids known as neodecanoic orversatic acid, a resin acid such as an acid derived from wood resin,e.g. abietic acid, a naphthenic acid, or a long chain aliphatic acidsuch as palmitic acid, stearic acid, oleic acid, linoleic acid,linolenic acid, arachidic acid, behenic acid or tall oil fatty acid, oran aromatic acid such as for example benzoic acid or an alkyl-, alkoxy-,amino-, halogen-, thio- or hydroxy- substituted benzoic acid, e.g.salicylic acid, anthranilic acid or chlorobenzoic acid, phthalic acid,terephthalic acid, or cinnamic acid. Preferably the acid is an aliphaticacid such as neodecanoic acid or a mixture of such an acid with anaromatic acid, e.g. benzoic acid, or an acid such as octoic acid,naphthenic acid or abietic acid in a molar ratio of 2.5:0.5 to 1:2,preferably about 2:1.

The metal organic compounds of the present invention may be made byheating together a mixture in the required proportions of

(1) the carboxylic acid,

(2) sources of the cobalt and nickel in the required ratio such as, moreespecially, an oxide, hydroxide or carbonate of cobalt and nickel,

(3) a borate ester of a lower alcohol, e.g. n-butanol, and

(4) an acid capable of forming a volatile ester with the lower alcoholresidues present in the said borate, e.g. acetic acid or propionic acid.

The volatile ester is distilled out of the reaction mixture as it isformed, preferably under reduced pressure. The acid (1) should beprereacted with the sources with cobalt and nickel (2) before the ester(3) is added.

The reaction temperature is typically in the range 50° C. to 250° C.,preferably about 150° C. to 200° C. The reaction is preferably carriedout under reduced pressure to facilitate removal of the volatile ester.

The metal organic compound in accordance with the present invention maybe associated with a borate of an element of group IA or IIA of theperiodic table, i.e. an alkali metal or alkaline earth metal. Suchborates may be present at a concentration of up to 20% by weight of themetal organic compound. Suitable borates include sodium borate,potassium borate, calcium borate and magnesium borate.

The metal organic compound may also be associated with micro-crystallinewax and/or process oil to facilitate incorporation in a rubber skimstock.

The metal organic compounds of the present invention are useful inrubber skim stock as adhesion promoters. For this purpose they may beincorporated into such rubber skim stock along with conventional rubbercompounding ingredients. The metal organic compound may be present in anamount between 0.2 and 2 parts by weight per 100 parts by weight ofrubber and preferably the metal organic compound provides about 0.2 to 4parts by weight of the stated combination of cobalt and nickel per 100parts by weight of rubber.

The invention is illustrated by the following Examples, in whichExamples 1, 2 and 3 are comparative and Examples 4 to 11 describes thepreparation of a metal organic compound in accordance with the presentinvention.

EXAMPLE 1

Cobalt boro neodecanoate

283 g of cobalt hydroxide containing 62.5% by weight of cobalt wasdispersed in 525 g of neodecanoic acid. Heat was evolved by the reactionand when the mixture had begun to cool down, 222 g of propionic acid wasslowly added over 30 minutes and the temperature of the reaction mixturewas adjusted to 95° C. After 1 hour at this temperature the mixture washeated to 190° C. and vacuum (28 mm Hg) was applied to facilitateremoval of the water present in the reaction mixture. n-Butyl-o-borate(230 g) was then added slowly, following which the temperature wasraised to 220° C. The n-butyl propionate formed was distilled out of thereaction mixture in vacuo. The product obtained, cobalt boroneodecanoate (786 g), contained 22.5% by weight of cobalt.

EXAMPLE 2

Nickel boro neodecanoate

561 g of nickel carbonate paste containing 31.4% of nickel was dispersedin 525 g of neodecanoic acid. The reaction mixture was heated to 60° C.and propionic acid (222 g) was then slowly added. After the propionicacid addition was complete, the mixture was heated at 95° C. for 1 houror until carbon dioxide ceased to be evolved. The mixture was thenheated to 190° C. under vacuum (28 mm Hg) until all the water formed inthe reaction had been removed. n-Butyl-o-borate (230 g) was then slowlyadded, and the reaction mixture was heated to 220° C. in vacuo so thatthe n-butyl propionate formed distilled out the reaction mixture. Theproduct obtained, nickel boro neodecanoate (880 g), contained 20% ofnickel.

EXAMPLE 3

100 g of the product of Example 1 was mixed at about 50° C. with 56 g ofthe product of Example 2 to yield 156 g of a mixture containing 14.4% ofcobalt and 7.2% of nickel.

EXAMPLE 4

196.4 g of cobalt hydroxide (60% Co) and 195.6 g of nickel carbonatepaste (30% Ni) were mixed with 525 g of neodecanoic acid and the mixturewas heated to 60° C. Propionic acid 222 g was then slowly added. Oncompletion of the addition of the propionic acid the mixture was heatedat 95° C. for one hour or until carbon dioxide ceased to be evolved. Themixture was then heated to 190° C. under vacuum (28 mm Hg) to removewater formed in the reaction. n-Butyl-o-borate (230 g) was then slowlyadded and the reaction mixture was heated to 220° C. under vacuum toremove the n-butyl propionate as it was formed. The product (841.7 g)contained 14% by weight of cobalt and 7% by weight of nickel.

EXAMPLE 5

128.7 g of technical grade nickel carbonate (45.6% Ni) was mixed with210 g of neodecanoic acid and 259 g octoic acid and the mixture washeated to 75° C. 196 g of cobalt hydroxide (60.1% Co) was then added andonce the exotherm had subsided, propionic acid 244 g was slowly added.On completion of the addition of the propionic acid the mixture washeated at 95° C. for one hour or until carbon dioxide ceased to beevolved. The mixture was then heated to 190° C. under vacuum (28 mm Hg)to remove water formed in the reaction. n-Butyl-o-borate (230 g) wasthen slowly added and the reaction mixture was heated to 220° C. undervacuum to remove the n-butyl propionate as it was formed. The product(752.9 g) contained 15.9% by weight of cobalt and 7.8% by weight ofnickel.

EXAMPLE 6

350 g of neodecanoic acid and 350 g white sprit was heated to 75° C. 196g of cobalt hydroxide (60.1% Co) was then added and once the exothermhad subsided, propionic acid 163 g was slowly added. On completion ofthe addition of the propionic acid, the mixture was allowed to cool to30° C. 128.7 g of technical grade nickel carbonate (45.6% Ni) and 286 gnaphthenic acid was added and the mixture was heated to 75° C. Propionicacid 81.4 g was then slowly added. On completion of the addition of thepropionic acid the mixture was heated at 95° C. for one hour or untilcarbon dioxide ceased to be evolved. The mixture was then heated to 190°C. under vacuum (28 mm Hg) to remove water formed in the reaction andwhite spirit. n-Butyl-o-borate (230 g) was then slowly added and thereaction mixture was heated to 220° C. under vacuum to remove then-butyl propionate as it was formed. The product (966.4 g) contained12.5% by weight of cobalt and 6% by weight of nickel.

EXAMPLE 7

314 g of nickel propionate neodecanoate (18.7% Ni) was mixed with 175 gof neodecanoic acid, 286 g naphthenic acid and 400 g white spirit andthe mixture was heated to 75° C. 196 g of cobalt hydroxide (60.1% Co)was then added and once the exotherm had subsided, propionic acid 163 gwas slowly added. The mixture was then heated to 190° C. under vacuum(28 mm Hg) to remove water formed in the reaction and white spirit.n-Butyl-o-borate (230 g) was then slowly added and the reaction mixturewas heated to 220° C. under vacuum to remove the n-butyl propionate asit was formed. The product (978.3 g) contained 12.7% by weight of cobaltand 6% by weight of nickel.

EXAMPLE 8

Propionic acid 160 g was slowly added to 196 g of cobalt hydroxide(60.1% Co), 350 g of neodecanoic acid and 350 g white spirit. Oncompletion of the addition of the propionic acid, the mixture was cooledto 35° C. 122 g of benzoic acid and 128.7 g of technical grade nickelcarbonate (45.6% Ni) were added and the mixture was heated to 60° C.Propionic acid 80 g was then slowly added. On completion of the additionof the propionic acid, the mixture was heated at 95° C. for one hour oruntil carbon dioxide ceased to be evolved. The mixture was then heatedto 190° C. under vacuum (28 mm Hg) to remove water formed in thereaction and white spirit. n-Butyl-o-borate (230 g) was then slowlyadded and the reaction mixture was heated to 220° C. under vacuum toremove the n-butyl propionate as it was formed. The product (736 g)contained 15.6% by weight of cobalt and 8% by weight of nickel.

EXAMPLE 9

175 g of neodecanoic acid, 122 g benzoic acid and 350 g white spiritwere heated to 50° C. 196 g of cobalt hydroxide (60.1% Co) was thenadded and once the exotherm had subsided, 164 g of propionic acid wasadded quickly. On completion of the addition of the propionic acid themixture was heated to 150° C. 314 g of nickel propionate neodecanoate(18.7% Ni) was then added. The mixture was then heated to 190° C. undervacuum (28 mm Hg) to remove water formed in the reaction and whitespirit. n-Butyl-o-borate (230 g) was then slowly added and the reactionmixture was heated to 220° C. under vacuum to remove the n-butylpropionate as it was formed. The product (760 g) contained 15.8% byweight of cobalt and 7.9% by weight of nickel.

EXAMPLE 10

Propionic acid 164 g was slowly added to 196 g of cobalt hydroxide(60.1% Co), 350 g of neodecanoic acid and 350 g white spirit. Oncompletion of the addition of the propionic acid, the mixture was heatedat 100° C. for 30 minutes. The mixture was then cooled to 70° C. and 302g of abietic acid and 128.7 g of technical grade nickel carbonate (45.6%Ni) were added. Propionic acid 80 g was then slowly added. On completionof the addition of the propionic acid the mixture was heated at 95° C.for one hour or until carbon dioxide ceased to be evolved. The mixturewas then heated to 190° C. under vacuum (28 mm Hg) to remove waterformed in the reaction and white spirit. n-Butyl-o-borate (230 g) wasthen slowly added and the reaction mixture was heated to 220° C. undervacuum to remove the n-butyl propionate as it was formed. The product(946 g) contained 12.5% by weight of cobalt and 6.6% by weight ofnickel.

EXAMPLE 11

175 g of neodecanoic acid, 302 g abietic acid and 350 g white spiritwere heated to 70° C. 196 g of cobalt hydroxide (60.1% Co) was thenadded and once the exotherm had subsided 164 g of propionic acid wasslowly added. On completion of the addition of the propionic acid themixture was heated to 150° C. 314 g of nickel propionate neodecanoate(18.7% Ni) was then added. The mixture was then heated to 190° C. undervacuum (28 mm Hg) to remove water formed in the reaction and whitespirit. n-Butyl-o-borate (230 g) was then slowly added and the reactionmixture was heated to 220° C. under vacuum to remove the n-butylpropionate as it was formed. The product (943 g) contained 12.8% byweight of cobalt and 6.4% by weight of nickel.

The products of Examples 1 to 11 were tested as rubber adhesionpromoters as follows.

A rubber skim stock was prepared having the following composition:

    ______________________________________                                                         Part by Weight                                               ______________________________________                                        Natural Rubber SMR 10                                                                            100.00                                                     Peptiser (P.C.T.P.).sup.a)                                                                       0.12                                                       HAF Carbon Black N-326                                                                           55.00                                                      Zinc oxide         8.00                                                       Stearic acid       0.5                                                        Highly Aromatic Process Oil                                                                      3.00                                                       Antidegradant (6 pPD).sup.b)                                                                     2.00                                                       Accelerator (DCBS).sup.c)                                                                        0.7                                                        Insoluble Sulphur  4                                                          ______________________________________                                         .sup.a) Zinc salt of pentachlorothiophenol                                    .sup.b) N(1,3-dimethylbutyl)-N'phenyl-p-phenylene diamine                     .sup.c) N,NDicyclohexyl-2-benzthiazyl sulphenamide.                      

Vulcanisable compositions were prepared using the above rubber skimstock and the adhesion promoters described in Examples 1 to 11 above.Each promoter was added in a proportion to provide 0.15 parts by-weightof metal or mixture of metals per 100 parts by weight of rubber. Theadhesion promoters were added to the skim stock during mixing in a 1.5 llaboratory internal mixer and sheeted off on to a 2-roll laboratorymill. All the compositions were vulcanised to T₉₀ +six minutes at 153°C.

Adhesion tests were carried out using a modified static block pull testbased upon ASTM D2229 using an embedment length of 10 mm. Typical brasscoated steel tyre cord of the construction 2+2×0.25 from Bekaert wasused, each cord having a coating of brass with an average copper contentof 63.5%. Adhesion values are quoted as a percentage of the valueobtained with the product of Example 1. The results are given in Table1.

    ______________________________________                                        PROMOTER                                                                      PRODUCT OF EXAMPLE                                                                              UNAGED   HEAT AGED                                          ______________________________________                                        1 (comparative)   100      100                                                2 (comparative)   88.3     86.6                                               3 (comparative)   92.5     97.5                                               4                 105      125                                                5                 115      118                                                6                 113      121                                                7                 105      122                                                8                 98.6     122                                                9                 107      118                                                10                107      125                                                11                104      130                                                ______________________________________                                    

These results show that, whereas the mixture of cobalt and nickelcompound is less effective as an adhesion promoter both unaged and afterheat aging, than a compound based on cobalt only, the metal organiccompound of the invention containing both cobalt and nickel in the samemolecule is surprisingly more effective as an adhesion promoter than thecompound containing only cobalt both unaged and after heat aging.

We claim:
 1. A metal organic compound of average formula:

    B(OCoA).sub.m (ONiA).sub.3-m

where the A radicals are the same or different and each is a residue ofan aliphatic monocarboxylic acid of 7 to 24 carbon atoms, a resin acid,a naphthenic acid, or an aromatic carboxylic acid of 7 to 11 carbonatoms, not more than two thirds of the A radicals being a said aromaticcarboxylic acid residue, and m is 0.5 to 2.5.
 2. A metal organiccompound according to claim 1 wherein m is about
 2. 3. A metal organiccompound according to claim 1 wherein A is a residue of neodecanoicacid, alone or in admixture with one or more of octoic acid, naphthenicacid, benzoic acid, and abietic acid.
 4. A metal organic compoundaccording to claim 1, associated with up to 20% by weight of a borate ofa metal of group IA or IIA of the periodic table.
 5. A metal organiccompound according to claim 1, associated with microcrystalline waxand/or process oil.